We're coming up on the 15th anniversary of the worst terrorist attack in American history. In 2001 most people didn't use cellphones, so if you knew someone who worked in or around the World Trade Center, all you could do was wait. Names of people who were unaccounted for scrolled across the bottom of television screens for weeks.

Unfortunately, terrorist attacks continue to occur on a regular basis throughout the world. And it's not just terrorist attacks we have to worry about. There are also floods, hurricanes, tornados, earthquakes and other natural disasters.

But thanks to Facebook, at least we have a way of checking on our friends and family living in the areas where these catastrophes are happening. The social media site is making this feature more accessible.

"Safety Check" is a Facebook function that allows people to mark themselves as safe during emergencies. When an earthquake shook Italy or when tornadoes tore through Indiana, citizens were able to notify all of their Facebook friends at once to say they were safe. If someone on your Friend list marks themselves safe, you receive a Facebook notification.